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US Patent 4499300
4-Vinylbenzeneacetic Acid
Abstract:
A multi-step preparation of 4-vinylbenzeneacetic acid from the readily available 1,4-diethylbenzene is described. The method uses cobalt (II) catalyzed oxidation of 1,4-diethylbenzene to 4-ethylacetophenone followed by oxidative rearrangement of the latter to 4-ethylbenzeneacetic acid, selective photochlorination, and finally base catalyzed dehydrochlorination of the latter to afford the title compound.
Example 1:
Oxidations were performed in a 50 ml flask fitted with a bottom-sealed sintered disk to effect air dispersion, a condensor, and a Dean-Stark trap. The flask was charged with 10g of 1,4-diethylbenzene while air flowed through the sintered disk at a rate between 125-250cc/minute. The cobalt compound used as a catalyst was added, and the contents heated to the desired temperature. Samples were withdrawn periodically and analyzed by gas-liquid chromatography to afford results in Table 1. The product, 4-ethyl acetophenone, was then isolated by the fractional vacuum distillation of the oxidation product mixture prior to its use as a reactant in the step.
Table 1:
Co(acetylacetate)2, 0.19 mol %, 105-110*C, 6hr, 38% conversion, 61% selectivity
0.19 mol %, 105-110*C, 16hr, 68% conversion, 63% selectivity
Co(neodecanoate)2, 0.19 mol %, 110-115*C, 6 hr, 49% conversion, 83% selectivity
Co(stearate)2, 0.19 mol %, 110-115*C, 9.5 hr, 73% conversion, 79% selectivity
Co(naphthenate)2, 0.26 mol %, 120*C, 6hr, 78% conversion, 72% selectivity
0.26 mol %, 120*C, 7 hr, 80% conversion, 68% selectivity
Co(toluenesulfonate)2, 3.00mol %, 90*C, 4 hr, 94% conversion, 44% selectivity
3.00mol %, 120*C, 2 hr, 0% conversion, 0% selectivity
Co(phthalocyanine)2, 0.26 mol %, 120*C, 2 hr, 26% conversion, 81% selectivity
0.26mol %, 120*C, 5 hr, 26% conversion, 81% selectivity
Example 2:
Preparation of 4-ethylbenzeneacetic acid
A 300ml ,3-neck flask with mechanical stirring, condensor, dropping funnel and Dean-Stark trap was charged with 66.9g (0.45mol) of 4-ethylacetophenone, 62.1g (0.71mol) of morpholine, and 22.8g (0.71mol) of sulfur. The contents were heated to 135-140*C under nitrogen, in some cases with removal of water. After about 3 hours, the mixture was cooled to about 40*C and about 120g of 20% aqueous sodium hydroxide was added with stirring. This mix was then heated to reflux and stirred for about 9 hours. After the reaction mix was cooled some of the morpholine and water were distilled off at 90-100Torr. To the residue at 60*C, was added slowly with stirring 50ml of conc. HCl acid brought to boiling and the hot reaction mass was stirred for about 1 hour. The solid, which is a mix of mainly the formed acid and sulfur, was collected with a 15% aqueous solution of sodium bicarbonate. The filtrate was then heated to boiling, decolorized with carbon, filtered and repeated. The solid was washed with hot water and the combined filtrates were acidified with conc. HCl acid to precipitate the 4-ethylbenzeneacetic acid. Without water removal in the reaction, 65% yield of the product is obtained and 100% of the morpholine can be recovered. Whereas, without the removal of water in the reaction, a 72% yield of the product is obtained and 0% of the morphonline can be recovered.
Example 3:
Preparation of 4-(1’-chloroethyl)-benzeneacetic acid
A solution of 4-ethylbenzeneacetic acid in either carbon tetrachloride or chloroform was reacted with chlorine while being irradiated with ultraviolet light.
Sample A: 0.01 mol reactant, 0.01 mol Cl2,15ml CCl4, 0.33 hr, 50% conversion, 100% selectivity
Sample B: 0.04 mol reactant, 0.04 mol Cl2, 70ml CCl4, 0.33 hr, 64% conversion, 80% selectivity
Sample C: 0.183 mol reactant, 0.19 mol Cl2, 200ml CHCl3, 1.25 hr, 52% conversion, 100% selectivity
Sample D: (Sample 3 continued for another 0.19m Cl2) 0.38 mol Cl2
Note: Selectivity of monochlorination at the benzylic carbon of the ethyl group is quantitative up to about 50%
Example 4:
Dehydrochlorination of 4-(1’-chloroethyl)-benzeneacetic acid
To a solution of 4-(1’-chloroethyl)-benzeneacetic acid in methanol may be added about 5 molar portions of sodium methoxide. The mix is stirred with gentle heat (about 50*C) for several hours. The cooled solution may then be acidified with a slight excess of 5% aq. HCl acid and extracted with ether to give the product, 4-vinylbenzeneacetic acid.
References Cited:
US Patent 4362891
